Components for use in large-scale concrete slab constructions

ABSTRACT

Structural reinforcing members are supplied for use in resisting shear forces within larger construction projects using reinforced concrete, along sites where strengthening ribs or beams between formers are to be created. The members also force the channels apart and maintain the reinforcing therein before curing at predetermined dimensions and spacings. A variant provides reinforcing cages that can be put together on the site for maintaining multiple reinforcing rods. The cages of different beams can intermesh at rib cross-over points. Example cages are eight-bar cages where each bar is made of 1.25 inch diameter reinforcing steel. During assembly the bars are held in place by the members with the assistance of gravity so that relatively little linking together of the reinforcing parts is required.

FIELD

This invention relates to building construction, to the provision of reinforcement for concrete structures, and in particular to structural components for incorporation in reinforced concrete masses to become built structures such as floors, buildings, bridges, or roads.

BACKGROUND

Concrete is a widely used cold-castable “liquid stone” used as a building material. After the reactions involved in setting and curing have taken place it has good compressive strength but relatively poor tensile and shear strength, so rods of reinforcing iron are cast into masses of concrete in order to restore tensile and shear strength. For use in mainly single-storey domestic housing floors poured as single slabs, the inventor has previously described a floor construction technique using buried void formers (made from a foam plastics such as polystyrene foam) to form a matrix of stiffening beams in the spaces left between the formers, using the inventor's stirrups to place reinforcing iron within the rods, in order to provide a stiff concrete floor for an optimised amount of materials. The void formers may have useful thermal insulating properties. Instead of void formers, other types of formers that contain the wet concrete within intended spaces may be used in some constructions.

The bent-wire stirrups (also called spacers) keep the formers apart and hence define the minimum width of concrete that will comprise each stiffening rib and also serve to hold the reinforcing iron and the void formers in place until the concrete has been poured and has set within each channel that is deliberately formed between the void formers. Other items such as pipes may be tied on to the stirrups. The entire working surface of the concrete floor is also provided with buried reinforcing mesh in typical floors. Single-pour concrete slab floors are often laid upon the ground (or grade as it is called in North America).

The final result after pouring and curing the concrete is a slab having a surface layer of concrete completely covering a reinforcing mesh layer that together have sufficient strength to resist predicted point loadings in particular, and below those is a crisscrossed array of deep concrete ribs each including reinforcing bars, separated by voids, together having sufficient strength to avoid failure of the slab as a whole. There is usually an outer border also made of a deep concrete rib including reinforcing bars. The design of each slab should be specified by an engineer in order to provide a desired strength and the procedure may be checked immediately before pouring in order to verify that channels of a desired width depth and length, containing iron bars in the correct positions within, are present. In contrast with the present structural invention the channels formed with the prior-art stirrups are small and weak (though appropriate for the job), and would lack the required ability to adequately withstand the stresses experienced in a larger construction.

This construction procedure is comparatively quick, has low labour costs, such as by reducing the amount of tying-together of reinforcing with wire, and the cost of raw materials is minimised. Use of these stirrups sharply reduces the labour content of a floor.

In relation to larger constructions, another laborious prior-art practice which is overcome by means of the present invention is that of assembling large cage structures of iron reinforcing bars, frames, and tie wire (or welds) typically off-site and then bringing them to the job and placing them in or on the structure that is to become reinforced concrete using a crane. Problems associated with this technique include the matter of creating cage structures of just the right size (let alone possible distortion during transport and placement) and of moving the heavy, large, and not particularly strong structures safely and conveniently to their final positions.

In this invention the term “structural stirrup” or “structural spacer” generally refers to a stirrup in which the material of the stirrup itself is capable of resisting shear stresses applied to a beam or rib of reinforced concrete in which it is implanted.

OBJECT

It is an object of this invention to provide components and a process for the construction of floors made from reinforced concrete capable of withstanding relatively high loadings, or at least to provide the public with a useful choice.

STATEMENT OF INVENTION

In a first broad aspect this invention provides structural components for use as part of the reinforcement of a reinforced concrete structure, wherein the components serve to dictate the dimensions of strengthening beams or ribs of concrete to be formed as part of the structure by delimiting and occupying spaces between rigid formers that will contain the concrete after pouring.

Preferably also the components provided are capable of determining the placement of reinforcing bars of metal within the strengthening beams or ribs of concrete by providing attachment points for supporting said reinforcing bars at predetermined positions until casting is complete.

Preferably also the components provided are capable of serving as structural reinforcement components orientated in order to resist shear stress applied to the strengthening beams or ribs of concrete.

Preferably each component is formed from metal.

Preferably each component is made of a stiff metal rod bent into a desired shape. A preferred stiff wire is steel rod in the 5 to 12.5 mm range, although the material used to form structural members is preferably of steel of a comparable thickness to that of the bars used in the construction. Optionally the steel rod is provided with a surface treatment capable of inhibiting corrosion.

In one option, the components are used along the strengthening beams or ribs of concrete as a series of single components and each single component includes (a) more than one attachment points each for a reinforcing bar of a reinforcing structure held at a predetermined position, and (b) includes at least one attachment point for location of the component with respect to an adjacent former so that each single component is capable of holding said reinforcing bars at predetermined positions with respect to the adjacent former and (c) includes sufficient internal tensile strength to serve as a structural element of the reinforcing structure.

In another option, the components are used as members of a group of components used along the strengthening beams or ribs of concrete as a series of groups of components for assembly into part of the structure during construction, and each group of components after assembly includes (a) more than one attachment points for more than one reinforcing bars each held at a predetermined position, and\(b) at least one attachment point for location with respect to an adjacent former so that each single component is capable of holding said reinforcing bars at predetermined positions with respect to the adjacent former, and (c) each group of components after assembly serves as a cage assembly capable of holding said reinforcing bars at predetermined positions.

In a related aspect the invention provides a set of components for use as a group in reinforced concrete structures; the set including an upper bar support, a lower bar support and channel spacer, a lower cage stirrup, and an upper cage member; all to be used as spaced-apart sets in conjunction with reinforcing rods placed horizontally within channels.

Preferably the group comprises an “n-bar cage” where n may be from two to sixteen bars of reinforcing rods.

In a second broad aspect this invention provides a method for assembly of a group of components as previously described in this section between formers and along an intended strengthening beam or rib, including the steps of: (a) placing non-structural “pod spacers and bar organisers” along the channel in order to to locate and hold the void formers in place during later component placement, and thereby to maintain the channel width, (b) placing a structural “top hat” deep bar-holding bent wire shape with sufficient depth to support a first, lower layer of bars at the deepest level, alongside each pod spacer and bar organiser, (c) placing a deep array of structural reinforcing rods in the grooves provided by a series of pod spacers and bar organisers, (d) placing a shallow non-structural pod spacer and bar organiser, (e) placing a second, shallow array of structural reinforcing rods, (f) placing an inverted “U” structural element to serve as part of the cage over the shallow array of reinforcing rods, and then (g) fixing the structural elements to each other such as by tying or welding, so that the assembly is ready for receiving wet concrete and providing reinforcement once the concrete has cured.

Preferably the respective arrays of reinforcing rods are installed so as to cross over each other at positions where beams of reinforced concrete are intended to intersect, thereby creating interlocking reinforcing cage assemblies at the site.

Preferably, where intersection of respective arrays of reinforcing rods is expected, the groups of components for use in a first set of beams is made longer than the groups of components for use in a second, intersecting set of beams by about the diameter of the reinforcing rods, so that the arrays of reinforcing rods may cross over each other without being bent.

Optionally the upper lengths of reinforcing iron are placed to lie above the reinforcing mesh and below the surface of the concrete.

Preferred Embodiment

The description of the invention to be provided herein is given purely by way of example and is not to be taken in any way as limiting the scope or extent of the invention. Variations which would be obvious to a skilled reader are to be considered as forming part of the invention.

DRAWINGS

FIG. 1: is a diagram showing a section across a reinforced channel according to Example 2 of the the invention.

FIG. 2: is a perspective diagram taken from a photo to show reinforcing bars placed in a channel, according to the invention.

FIG. 3: is a perspective diagram also taken from a photo from within a channel, showing perpendicular groups of reinforcing bars crossing over each other.

FIG. 4: is a diagram showing a structural stirrup according to Example I of the invention.

FIG. 5: illustrates example prior-art components—FIG. 5 a shows a non-structural stirrup and FIG. 5 b shows a piece of reinforcing iron bent to provide a four-bar cage.

FIG. 6: is another diagram showing a two-bar structural stirrup according to the invention.

FIG. 7: is another diagram showing a structural stirrup for use along a rib line where the floor surface height is stepped.

FIG. 8: is another diagram showing a structural stirrup for use in the perimeter of a foundation.

The inventor's original stirrups (alternatively called spacers) intended for small constructions are symmetrical bent metal objects, typically as shown in prior-art FIG. 5 a, showing a non-structural stirrup with all bends in a single plane. There is but one portion adapted for holding a reinforcing iron bar—the lowest part; the corner at 20 so that the eventual concrete rib (typically 6 inches across and 12 inches deep) will include one central length of reinforcing iron. Such ribs have significantly less structural strength as compared with those made of larger (eg 268 mm wide, at least 260 mm deep) concrete ribs having structural applications and including more, larger bars at a variety of heights. Non-structural ribs are suitable for single-floor dwellings with floating slab-on-grade floors, whereas structural ribs are required wherever the anticipated loads are higher.

The preferred manufacturing technique for these bent metal objects is to use a numerically controlled wire-bending machine, so long as available machines have the strength to cold-bend the desired thickness of rod. Another way to make stirrups from any thickness of iron rod is by heating the rod to red heat, then bending it around pegs on a jig, and preferably coating the finished product with an anti-corrosion treatment. Stirrups can also be made by casting, moulding, cutting, or any other method known to one skilled in the art, and the materials selected can be selected from a large range of materials offering sufficient strength as required during the period of construction of the concrete structure.

All stirrups along the same channel usually have the same shape and are laid at typically 18 inch spacings. Both end portions of the prior-art stirrup of FIG. 5 a —403 and 404 (occasionally only one end—for use at perimeters, as in prior-art FIG. 8) terminate in a downwardly projecting section 401 and 402 used to impale and fix the stirrup in relation to a void former. (Options may be adapted for use with other forms of fastening, such as holes through flattened end portions for use against timber formers with nails or screws). Between the end portions there is a channel defining portion, comprising a downwardly projecting “U” shape 405-501-406 which in use occupies a channel that is typically 6 to 8 inches wide between adjacent void formers. Within the channel defining portion there is one or sometimes more downwardly directed recesses 501 for supporting horizontal reinforcing bars that will be laid to pass along the length of the channel.

The recess or recesses are usually placed so that the bars will lie at controlled positions deep in the interior of the concrete rib that will be formed in the channel when concrete is poured within. The stirrup prevents the bar(s) from being too close to the base or to any exterior surface. The cover of concrete provides strength and may be mandated for protection against corrosion. Use of a rod material as the material for the stirrup minimises any interruption to the integrity of the concrete rib along its length—as compared for example to plastics moulded versions. The strength required of the stirrup is for temporary holding purposes only.

EXAMPLE 1 Structural Stirrups

Structural stirrups, also known as structural spacers because they space apart bars and void formers (or other formwork), provide extra points for locating lengths of reinforcing iron within a channel so that the resulting rib will have a structurally useful degree of strength. Examples are shown as FIGS. 4, 6, 7 and 8. They include bends to locate bars of reinforcing iron at a range of depths. The structural stirrup of FIG. 4 includes downward-directed bends at 409, 401 and 415 that can hold bars by gravity alone, avoiding the labour costs of placing wire ties. Extra bars could be tied in at 407 and 408, providing either a three-bar reinforced rib, or a five-bar reinforced rib.

FIG. 4 shows a typical structural component, according to the invention, for use in reinforced concrete structures. (Dimensions are given by way of illustration only). This component is made of 6.4 mm diameter steel rod, formed by bending in a numerically controlled bending and cutting machine. Although that method might seem unduly complex or slow, it is automated and the versatility of the machinery suits the wide variety of particular shapes and sizes that are required from time to time for these components. The components to be described by example here illustrate the principles of the invention but by no means the entire possible range of examples.

Note that the example structural stirrup shown in FIG. 4 includes the following components: downwardly projecting free ends 401, 402 intended to impale and hold (with the help of gravity) the void formers and the reinforcing together as one unit until locked in place by poured concrete, separated by a bridging portion including two horizontal sections 403, 404 which lie over the surface of the void former thereby holding the formers down during pouring and maintaining a standardised height for the structural stirrup; two vertical contact sections 405, 406, for defining and maintaining the space between void formers; two central raised “bar-holding corner” portions 407, 408, for locating lengths of reinforcing rod—(the inside of bends made in the originally straight rod); and to each side of each, a depressed holding corner portion 409, 410 which is maintained at at least a certain distance inside the channel between adjacent void formers by the descending limbs; by the sloping separators 411, and 412. The spacing between the structural reinforcing rods in the vertical axis is maintained by the straight sections 413, 414. The “valley” 415 may be used as a place for a further length of reinforcing rod or this can be regarded as a distance-maintaining separator between rods 407 and 408 and as a depressed zone where a bar of the reinforcing mesh can pass. Similarly the distance between 405 and 406 determines the width of the channel between the voids which is to become filled with concrete including the reinforcing materials held by the structural stirrups.

It will be apparent that each structural stirrup is made of an elongated material having (a) ends, (b) straight portions, and (c) bent portions. Most bends are formed in a single plane although bends can be made in any plane and the examples may make use of advantages of bending in other planes. Note that although the present embodiment has bent portions which are made by actually bending a straight piece of stock, the aware reader will be able to see that stirrups having flexures (corners) fulfilling these functions might be made by other processes such as injection moulding a plastics material into a die, by casting molten metal, by cutting from a sheet, by slumping, or by bolting, welding, or otherwise fixing together a number of parts into stirrups. Use herein of the verb “to bend” or its variants does not preclude alternative manufacturing processes.

In use, four lengths of reinforcing iron tied to this structural stirrup at corners 407, 408, 409 and 410 have about the same effect on tensile and shear strength as would four lengths of reinforcing iron provided as a prior-art four-bar cage (FIG. 5 b) but with the advantages that the stirrup is a structural element, and the substitute for the cage provided by the invention is supported from the void formers so that the position of the bars and of the entire cage within the rib of concrete is better defined (for example they must lie at least 50 mm inside the concrete beam according to New Zealand building code requirements, to reduce corrosion and enhance function), and little or no wire tying is needed. In some situations there may not be any nearby void formers, when the prior-art four-bar cage can be used to hold the rods together across a gap. As will be described later, there are advantages in creating an equivalent to a cage on the job rather then as a prefabricated component.

A suitable vertical separation between lengths of reinforcing iron may be obtained by having the upper pair of rods lying on or above the almost universally used reinforcing iron mesh (not shown) which is buried to 30 or 50 mm under the surface of the finished slab. Parts 407 and 408 of the structural stirrup poke through the mesh. Using the mesh to support the upper beams makes wire tying (if necessary) much easier than if the weight of the bars has to be supported during and after tying. If the upper corners are formed as functional rings then the mesh does not need to support the upper pair of bars which could make the labour of installation easier, as long as poking bars through holes is feasible. Functional rings could comprise a loop of about 1.5 turns, or the portion of the stirrup leading to the valley 115 could be brought sideways and down in a “fat U” profile rather than the “V” profile shown here, so that the surface profiles of corners 107 and 108 are closed.

Note that these structural stirrups also have a number of associated functions:

1. They define and keep open the channels between void formers before concrete setting.

2. They locate the void formers in position over the surface that is to become a concrete slab and hold them down by the weight of the iron bars onto the underlying damp course or other surface to prevent any inadvertent movement by the weight of the iron before pouring. This weight includes the weight of subsequently placed reinforcing mesh, usually (but dependent on application) 1/10 or ⅛ inch diameter iron rod, welded into mesh with 10 inch squares.

3. They accurately locate the heights, directions and horizontal locations of the reinforcing bars (iron) that provide the concrete slab with useful structural properties.

4. They can be used as frames to tie the reinforcing bars down, and to each other, at correct placements.

5. The highest corners (407, 408) which emerge above the plane of the reinforcing mesh in some versions can be used to tie down the mesh beneath the upper reinforcing bars.

The structural stirrup of FIG. 6 includes two bar holding bends only, at 601 and 602 within a concrete rib 4 ½ inches wide and about 10 inches deep. These bars are well separated in height, for extra flexural strength of the final construction. Because bend 601 is made to lie above reinforcing mesh, if used, and well above the upper surface of the void formers, if used, this stirrup is suited to use with relatively thick coverings of concrete over the void formers. (604 may also be used to hold a bar but it will lie rather too close to the edge of the concrete for approval by some building inspection authorities).

The structural stirrup 700 of FIG. 7 provides for up to five bars, at 703 and 707 held by gravity, 704, 705 and 706 (held with a tie), and the height difference between 703 and 707 increases the bar separation for extra strength. This stirrup also provides for a step change in concrete height by virtue of the lower height of horizontal portion 702 as compared to portion 701. Such a step change in floor height could have been specified in the plans for the construction. The height of the void former on the left (under portion 701) may be 4 inches higher than the height of the void former 702 on the right. This example illustrates the design freedom provided by use of numerically controlled manufacture.

The FIG. 8 asymmetrical structural stirrup 800 is intended to locate lengths of reinforcing iron within a perimeter channel around the outside of a slab-on-grade concrete floor. This type provides holding corners for three reinforcing bars placed at 804, 805, and 806 in specified relationships to the outer corner of the void former, thereby providing structural strength. Only one impaling end (801) at the end of horizontal 802 is provided because there will be no void former on the outside, but the stirrup at or about 807 may be stapled or otherwise attached to wooden or other formwork. located to the right of the stirrup so that the poured concrete is held in place. This diagram also shows the preferred extended, zig-zag limb 801 which enhances the grip of the structural stirrup into the void former and tends to minimise sideways deflection. Limb 803 may also be formed as a zigzag. The bends in 801 are not shown because they are made in a plane perpendicular to the plane of the illustration and to the rest of this stirrup. An about 10 inches (255 mm) wide rib of concrete is defined by means of this example structural stirrup.

EXAMPLE 2 Cage Constructions, Assembled on the Site

A further development of the present invention that is intended for significantly greater loadings is partly based on a non-structural stirrup as per FIG. 5 a, but with additional parts. Further, it resembles a cage structure, but one that is preferably assembled on site. Some functions of a simple stirrup, such as determination of the channel size are retained. By way of comparison, we first describe a prior-art four-bar cage structure illustrated as FIG. 5 b. In this cage, which has an indefinite length, four bars such as 502, 504, 505 and 506 are tied to a series of bent reinforcing iron bars 503 which serves to maintain the bars in a spaced-apart configuration after embedment in concrete, so that the resulting reinforcement has greater strength to resist torques. Larger cages would use stouter rods and have more of them.

This description and these drawings are based on a specific prototype, show an eight-bar cage, and refer to certain dimensions. The prototype is a demonstration intended to cater to one site's specifications. The experienced reader will be aware that floors (or road surfaces, etc) may be designed to various degrees of strength by the responsible engineers and hence wide variations in bar numbers, diameters, positions, and other variables can be imposed according to requirements while staying within the general principles of the invention.

The example of FIG. 1, also shown as an installation in perspective in photographs in FIGS. 2 and 3 is a mid-range size example of an on-site cage/stirrup composite that illustrates the principles of the invention. Several bent wire or bent rod items are grouped together in assemblies that are used repeatedly along a channel and which are linked, welded, or tied to at least some reinforcing bars laid along the channel. Usually an entire floor would be poured as one slab once a number of cage/stirrup assemblies had been installed, although if the resulting floor is considered too large in relation to potential shrinkage and expansion of the concrete, expansion joint formers may be inserted as is standard practice in the industry. It is convenient to describe the structure in a preferred order of assembly.

-   1. The first step, after laying out, is to place void formers 102,     103 made of a material such as a polystyrene foam of an appropriate     degree of density along each side of each channel. Preferably each     void former fills the area between one channel and a neighbouring     parallel channel, while usually including a second array of channels     oriented perpendicular to the first channels, herein termed the     first array. (Note that the cage/stirrup composite structure may be     tied to other structures in a construction that does not include     void formers as such, such as a construction dug into the ground as     a criss-crossed array of trenches, or one using boxing made of wood     or cardboard. The cage aspect of the invention does not dependent on     void formers for its operation). Void formers (or other structures)     may be raised above the grade on supporting blocks 104, or on piles,     in part to provide a level top surface at 103, 102 and in part to     provide a deep space to receive concrete at 117. Damp-course     material may be included below, as is standard practice, or if a     suspended floor or other structure is being built, a lower temporary     layer will have been put in place. Not shown here is the preferred     option of using a disposable hard board (such as “Hardibacker (TM)”     or plywood) as a protective surface over the top of the void formers     so that the pods can better withstand the normal stresses of     labourers (even vehicles) moving over them while carrying bars and     other things during assembly of the floor. -   2. The first laid components, known as “pod spacers and bar     organisers” serve to locate and hold the void formers in place     during later component placement. These first-laid components are     visible between impaling end 107A and 110 in FIG. 1, including     downward-projecting limbs 107 and 109 that define the channel width     by preventing a closer approach of the void formers, and at least     one but typically downwardly four bar position-defining bends 108     along a wiggly part of this component. (This component being thinner     is easier to bend freely than the next component to be inserted). We     prefer that the length of all droppers holding “east-west”     orientated bars is about one bar diameter longer than those holding     “north-south” droppers (or vice versa) so that bars can cross over     each other without impediment. Hence it can be seen that the     dimensions of the various bent metal “bridging elements” sets the     positions of the reinforcing bars inside. The height of the valleys     and hence the ironwork above the grade is something normally     determined by the engineer or by ordinances. A typical suitable     spacing along each channel is for example 2 to 4 feet (0.6 to 1.2     metres) apart. -   3. The second laid component is for weight-bearing purposes It is a     deep bar-holding bent wire shape having an inverted top hat profile     113-113 lacking the end impaling sections, and with the depth of the     “U” sufficient to locate the recesses for holding a first, lower     layer of bars at the deepest level, is placed alongside each     stirrup. This heavier bar serves to support the weight of the     reinforcing material and to transfer the weight to the adjoining     void formers (or other structure). It is bent so that the bars lying     in the bar position-defining bends 108 are in contact with this bent     wire shape. This bar is not required to define the channel width     although it may do so. The first and second components may be     combined into one component. -   4. The third laid component is a deep array of reinforcing rods     105A, 105B, 105C, 105D which are possibly cut to length and are now     placed in the channel and may be tied down. (Tying down may be a     regulatory requirement although the bars are not likely to move on     account of their weight). The lower set of bars, to lie under the     other perpendicular set, are of course laid first. These bars are     relatively heavy but each is compatible with handling by two or more     men, unlike a finished cage, and a crane is not required. -   5. The fourth laid component is a shallow bar-holding bent wire     shape. Like the second laid component, this is made of a lighter     wire and is preferably bent to include impaling ends, for retention     during installation, and has a central series of at least one but     typically four bar position-defining bends 118. -   6. The fifth laid component is a shallow array of reinforcing rods     106A, 106B, 106C, 106D which are now placed in the channel and may     be tied down. Again, the lower set of bars, to lie under the other     perpendicular set, are of course laid first. These bars are     relatively heavy but each is compatible with handling by two or more     men, unlike a finished cage. -   7. The sixth laid component is the upper “U” section of the cage     119-119′ which is dropped down over the top set of bars. This item     is used to cover and retain the most shallow set of bars. It should     be fixed to the sides of the second laid component so that it will     not spring upwards for any reason and allow the upper bars, or     itself, to approach the surface of the intended pour of concrete. A     suitable fixing means is a wire tie at 115. We find it faster and     more convenient to use an arc welder to spot weld the cage     components together such as at 115, 116. If this is done the     structure becomes quite immobile. If anti-corrosion coatings have     been specified the weld should be sprayed with a zinc spray or     similar, once cooled. -   8. Normal practice is to cover the upper surface of the concrete,     over the entire area of the slab and including the void formers with     a reinforcing iron mesh, supported above the void former surface by     support blocks or devices known in the trade as“bar stools” that     support the mesh deep within typically 4 to 6 inches of concrete.     Then the assembly is ready for inspection and then pouring. Of     course, other items to be included within the concrete such as pipes     and cables should be placed before pouring. -   9. It will be appreciated that a middle layer of reinforcing bars     could also be placed in the channel if required.

As a result of this procedure, the channel is provided with eight substantial steel bars running along its length. These bars are variously known as “Reo bars, HD32, reinforcing material, or “Seismic 500” and each is about 1 to 1.5 inches in diameter. These replace a conventional “eight-bar cage” which under prior-art methods would have been made with wire tying outside the work site, trucked in, and lifted into position by crane. Four bottom bars 105A . . . 105D are positioned first, by placement on top of aligning structures placed in the channels at a suitable spacing such as 600 mm, 1 metre, or 1.2 metres apart. One structure is the bent wire “pod spacers and bar organisers” 107-109 in FIG. 1. The other structure is the “structural box cage stirrup” 111 in FIG. 1. Both structures are U-shaped and are supported by their ends (113, 113′ and 110) against the upper surfaces of the pods.

FIG. 2 is a perspective view (taken from a photograph) looking down on a channel including reinforcing according to the procedure and materials described previously in this section. This was an experimental prototype and some of the stirrups (e.g. 110) are temporarily lifted up on packers 201 to adjust the heights of the supported bars. 202 is a distant view of an intersecting channel and other numbers are as per FIG. 1.

FIG. 3 is a perspective view (from a photograph taken within the assembled channel), looking at an intersection of channels where the lower arrays of bars intersect. In prior art methods of making reinforced floors, this simple laying procedure resulting in intermeshed cages would not be feasible. The labourers do have to remember to lay the lower sets of bars first and preferably use longer or shorter stirrups 109 for both top and bottom sets of bars according to positions. Alternatively, different heights of bar chair may be used to support the bent stirrups. In FIG. 3, the lower sets of bars are in view (the top set 106A-D are only just visible). The set 105A . . . D corresponds to those of FIG. 1. The set 305 A-D is a second set arriving at the intersection at right angles. Again there is no need to tie or otherwise fix the bars together unless there is a small discrepancy to be overcome or if there is a regulatory requirement to tie.

Under prior art methods, bars would be cut and tied to bridging bars which pass by each other at an intersection. This significantly weakens the structure and takes time and labour units.

The large bars are usually about 30-60 feet long. They are best joined up by an end-to-end butt with a bridging rod tied (or welded) to both of them, over at least 2 feet overlap on each side.

It will be appreciated that two labourers can carry a large metal bar from a pile to an end-use site while they create the n-bar cages about the floor. Therefore there is no requirement to have a crane to work over the floor areas to handle pre-assembled four-bar or eight-bar cages.

VARIATIONS

There is wide scope for variation in sizes and shapes of spacers/stirrups for specific applications, and for locations of holding corners within any type of spacer, directed to controlled positioning of the bars in relation to the concrete rib, for specific tasks.

An engineer may specify a selected inter-spacer spacing along a channel, the number and size of the reinforcing bars to be used, and the position of each bar within the channel, in view of the cross-sectional area of the concrete in the beam, and according to structural requirements such as the expected load, plus safety margins while obeying the limits imposed by any standards or building codes in force at the site.

INDUSTRIAL APPLICABILITY AND ADVANTAGES

The advantages include:

-   1. reduced labour time (perhaps by about 80% labour reduction in one     estimate) during preparation of the reinforcing iron and hence     labour cost, as well as a reduced amount of undesirable jobs on the     site (because tying cages and beams is an unappealing job. The skill     level is lessened. The overall cost of a built structure is reduced. -   2. The method provides ease of specification, better assurance that     specifications are being followed, and is well adapted for     inspections such as before pouring. -   3. The four-bar, six-bar, or similar cages are constructed at the     position of end use within the trenches and do not need to be     trucked (by relatively ineffectively loaded trucks) to the site     already made up, and lifted into position by crane. -   4. “Seamless” intersections of four-bar, six-bar, or similar cages     in a first or “north-south” direction with four-bar, six-bar, or     similar cages running in the perpendicular or “east-west”     reinforcing bars can be created at the time of bars placement,     including crossing over of bars, while retaining structural     integrity. -   5. Use of a numerically controlled wire bender, or other rod shaping     means, allows good freedom when adapting the basic idea to specific     construction site requirements. -   6. The metal reinforcing is positively held within the concrete to     be poured. Potential “close approaches” to a perimeter of the body     of concrete can be anticipated and prevented by means of supports     (“bar chairs”) and/or by anti-corrosion treatment of metal at risk. -   7. This system does not impose any breaks along the length of the     reinforced rib, whereas some plastic prior art analogues having flat     profiles inevitably interrupt the concrete.

Finally, it will be understood that the scope of this invention as described and/or illustrated herein is not limited to the specified embodiments. Those of skill will appreciate that various modifications, additions, known equivalents, and substitutions are possible without departing from the scope and spirit of the invention as set forth in the following claims. 

1. Components to form part of the reinforcement for a reinforced concrete structure, wherein the components serve to (a) determine the dimensions of strengthening beams or ribs of concrete to be formed as part of the structure, by delimiting and occupying spaces between rigid formers that will contain the concrete after pouring, (b) dictate the placement of reinforcing bars of metal within the strengthening beams or ribs of concrete by providing clear attachment points for holding said reinforcing bars at predetermined positions, and (c) serve in themselves as structural reinforcement components orientated in order to resist shear stress applied to the strengthening beams or ribs of concrete.
 2. Components as claimed in claim 1 wherein each component is formed from metal.
 3. Components as claimed in claim 1 wherein the components are used along the strengthening beams or ribs of concrete as a series of single components (herein termed “structural stirrups”) and each single component includes (a) more than one attachment points for a corresponding reinforcing bar held at a predetermined position, and (b) at least one attachment point capable of locating the component with respect to an adjacent former so that each component is capable of holding said reinforcing bars at predetermined positions with respect to the adjacent former.
 4. Components as claimed in claim 1 wherein each component is used as a member of a group of components for assembly as part of the structure during construction, and each group of components after assembly includes (a) more than one attachment point for more than one reinforcing bars each held at a predetermined position, and (b) at least one attachment point for location with respect to an adjacent former so that each single component is capable of holding said reinforcing bars at predetermined positions with respect to the adjacent former, and (c) each group of components after assembly serves as a cage assembly capable of holding said more than one reinforcing bars at predetermined positions.
 5. A reinforced concrete structure including a cage assembly as claimed in claim
 4. 6. A reinforced concrete structure including intersecting cages constructed in position.
 7. A method for assembly of a group of components as claimed in claim 4 along the course of an intended strengthening beam or rib, between formers, including the steps of: a) placing deep non-structural “pod spacers and bar organisers” along the channel in order to locate and hold the void formers in place during later component placement, and thereby to maintain the channel width, b) placing a structural “inverted top hat” deep bar-holding bent wire shape with sufficient depth to support a first, lower layer of bars at the deepest level, alongside each pod spacer and bar organiser, c) placing a deep array of structural reinforcing rods in the grooves provided by the deep series of pod spacers and bar organisers, d) placing shallow non-structural pod spacer and bar organisers along the channel, e) placing a shallow array of structural reinforcing rods in the grooves provided by the shallow series of pod spacers and bar organisers, f) placing an inverted “U” structural element to serve as part of the cage over the shallow array of reinforcing rods, in alignment with the “inverted top hat” g) fixing the structural elements to each other, so that the assembly is ready for receiving wet concrete and providing reinforcement once the concrete has cured.
 8. A method as claimed in claim 5, further wherein at positions where beams of reinforced concrete are intended to intersect, the respective arrays of reinforcing rods are installed so as to cross over each other thereby creating and installing interlocking reinforcing cage assemblies.
 9. A method as claimed in claim 8, wherein should beams of reinforced concrete be intended to intersect, those groups of components for use with a first set of reinforcing rods oriented in a first direction is made longer in order to reach to a greater depth than the groups of component for use with a second, intersecting set of reinforcing rods by about the diameter of the reinforcing rods, so that the sets of reinforcing rods may cross over each other without bending. 